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package Ast;
use strict;
use vars qw/ $this $pack @endCodes /;
#-----------------------------------------------------------------------------
# This package is used to create a simple Abstract Syntax tree. Each node
# in the AST is an associative array and supports two kinds of properties -
# scalars and lists of scalars.
# See SchemParser.pm for an example of usage.
# ... Sriram
#-----------------------------------------------------------------------------
# Constructor
# e.g AST::New ("personnel")
# Stores the argument in a property called astNodeName whose sole purpose
# is to support Print()
sub New {
my ($this) = {"astNodeName" => $_[0]};
bless ($this);
return $this;
}
# Add a property to this object
# $astNode->AddProp("className", "Employee");
sub AddProp {
my ($this) = $_[0];
$this->{$_[1]} = $_[2];
}
# Equivalent to AddProp, except the property name is associated
# with a list of values
# $classAstNode->AddProp("attrList", $attrAstNode);
sub AddPropList {
my ($this) = $_[0];
if (! exists $this->{$_[1]}) {
$this->{$_[1]} = [];
}
push (@{$this->{$_[1]}}, $_[2]);
}
# Returns a list of all the property names of this object
sub GetProps {
my ($this) = $_[0];
return keys %{$this};
}
sub Visit {
# Converts each of this AstNode's properties into global variables.
# The global variables are introduced into package "main"
# At the same time, a piece of code is formed to undo this work above -
# $endCode essentially contains the values of these global variables
# before they are mangled. endCode gets pushed into a stack (endCodes),
# which is unwound by UnVisit().
local ($this, $pack) = @_;
my $code = "";
my $endCode = "";
foreach my $k (keys %{$this}) {
my $glob = $pack."::".$k;
if ( defined $$glob ) {
if ( ${$glob} ne "" ) {
$$glob =~ s/\'/\\\'/g;
}
$endCode .= '$'.$pack.'::'.$k. " = '".$$glob."';";
} else {
$endCode .= '$'.$pack . "::". $k . ' = "";';
}
$code .= '$'.$pack . "::" . $k . "= \$this->{\"$k\"};";
}
push (@endCodes, $endCode);
eval($code) if $code;
}
sub UnVisit {
my $code = pop(@endCodes);
eval($code) if ($code);
}
1;
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